Device for Compensating Variations in Tension and/or for Adjusting the Tensile Stress on a Conveyed Flexible Material Strand

ABSTRACT

A device for compensating variations in tension and/or for adjusting the tensile stress on a conveyed flexible metal material strand, in particular a metal strip, having at least one movable dancer roll which can be wound around by the material strand. At least one dancer roll can be displaced along a path inclinable to the perpendicular, wherein the inclination angle of the path can be adjusted by means of an adjustment unit.

The invention relates to a device for compensating variations in tension and/or for adjusting the tensile stress on a conveyed flexible metal material strand, in particular a metal strip having at least one movable dancer roll which can be wound around by the material strand.

Devices for compensating variations in tension and/or for adjusting the tensile stress, for example in thermal strip treatment plants, using movable deflector rolls, so-called dancer rolls, have been known for years from the prior art and have proved themselves many times in practice.

A dancer roll arrangement comprises a roll which is integrated into the strip flow of a strip treatment plant and can be acted on by a certain force, this roll forming a loop in the strip, the length of which loop changes with the position of the roll. By means of this movability, even short-term variations in the strip tension can be compensated. In order to adapt the strip tension to different operating conditions, it can be necessary to adjust the force exerted by the dancer roll on the strip, wherein thick and wide strips require higher forces exerted on them by the dancer roll than sensitive, thin strips. In fact, in the case of thin strips, the force exerted by the dancer roll on the sensitive strip has to be restricted in order to prevent the strip material from becoming damaged.

In this connection, it is known from the prior art to at least partly compensate the weight force of the dancer roll and of its bearing, which is exerted on the strip material, by counterweights or actuators, in the form of hydraulic or pneumatic cylinders, acting on the dancer roll. In the case of counterweights, the problem arises that the inert mass of the dancer roll arrangement is further increased by the counterweight, whereby this counterweight can no longer satisfactorily compensate short-term variations in strip tension owing to high inertia forces. When very low strip tensions are to be achieved, breakaway forces and torques to be applied in the case of actuators become noticeable in a negative way, since they also impede compensation of short-term variations in the strip tension.

In FIGS. 1 to 5, typical dancer roll arrangements known from the prior art are illustrated.

Taking this as the starting point, the invention is based on the object of specifying a device for compensating variations in tension and/or for adjusting the tensile stress on a conveyed flexible metal material strand, in particular a metal strip, which is very simply constructed and can consequently be integrated with little effort into existing treatment plants for metal material strands, in particular material strips. In addition, the device is to allow even short-term variations in tension to be compensated in thick and heavy material strands as well as thin and sensitive material strands, wherein a change in the material strands during continuous operation with a corresponding adjustment to the tensile stress is also to be possible without difficulty.

The object is achieved according to the invention with a device according to the preamble of claim 1, in that the at least one dancer roll can be displaced along a path inclinable to the perpendicular, wherein the inclination angle of the path can be adjusted by means of an adjustment unit.

The present invention is based on the notion that by means of a suitable inclination of the direction of movement of the dancer roll to the perpendicular, and thus to the weight force vector of the dancer roll, the strip tension can be precisely adjusted without additional weights increasing the inert mass of the arrangement and without actuators.

In terms of the present invention, metal material strand is understood to be wire-shaped or strip-shaped material, strips for transporting goods of different types and also metal ropes, wires and the like.

By correspondingly adjusting the inclination angle of the path, along which the dancer roll can be displaced, the full weight force of the dancer roll and of its bearing can, for example in the case of thick, heavy material strands, be exploited to produce a sufficient strand tension (strip tension), namely by reducing the inclination angle to zero, so that the dancer roll can be displaced in the vertical direction. With thin, very sensitive strips, the inclination angle can be correspondingly increased up to nearly 90°, so that the weight force of the dancer roll and of its bearing has practically no effect any more on the strand tension and this is accordingly minimal. The tensile force effective in each case can be determined from the weight force of the dancer roll and of its bearing by a simple trigonometrical equation. The equation corresponds to the downhill-slope force on an inclined plane and is calculated as

F _(z) =F _(G)·cos φ

with F_(G)=weight force of the dancer roll and of its bearing; φ=inclination angle of the path to the perpendicular) (0<φ<90°.

By, at the same time, supporting the dancer roll as frictionlessly as possible on the path, inclinable to the perpendicular, in addition to precisely adjusting the strand tension, at the same time variations in the path tension of the flexible material strand can be effectively compensated.

Preferably, the adjustment unit is designed to be controllable for adjusting the inclination angle of the path, i.e. a change in the inclination can be triggered by a corresponding control command during automated operation of a treatment plant for the metal material strands, in particular of a strip treatment plant. This is then particularly advantageous if a change in the material strand occurs during continuous operation of the treatment plant, wherein the ends of both strands are attached to one another.

According to a further advantageous embodiment of the invention, the dancer roll is arranged between two deflector rolls, so that in operation the flexible metal material strand together with the dancer roll forms a strip loop. With such an arrangement implemented many times with known dancer rolls, in particular in strip treatment plants, it has proved to be particularly advantageous if with the dancer roll, which according to the invention can be displaced on a path inclinable to the perpendicular, its wrap angle can be kept relatively constant both during dancer movement along the inclinable path and with an adjustment of the inclination angle, so that the tensile forces exerted on the material strand can be precisely controlled at all times.

According to a further embodiment of the invention, the path, inclinable to the perpendicular, is linear. With a strictly linearly designed path, for example a linear guide, the inclination angle set to the perpendicular is precisely maintained irrespective of the current position of the dancer roll in the dancer movement, so that the tensile force continuously exerted on the flexible material strand exactly corresponds to the value preset by the choice of the inclination angle of the path. In terms of design, this can be accomplished, for example, by the bearing of the dancer roll being essentially frictionlessly guided on a linear guide. Linear roller guides are particularly suitable for this purpose. Here, differently designed linear guides can also be employed as “linear guides”, for example roll guides and rail guides of all kinds as well as slide guides or air cushion guides or magnetic guides. For example, the shaft of the dancer roll can be guided in a linear slot or in a gap between two carriers aligned parallel to one another.

According to a further embodiment of the invention, the adjustment unit can comprise an electromechanical drive, in particular a spindle drive, or a regulating element, in particular a hydraulically or pneumatically operating cylinder, so that the linear guide can be pivoted about a pivot point to adjust the inclination angle of the path. Such a pivoting mechanism can be easily produced in terms of construction and, in addition, can be integrated into a general machine control system without difficulty.

As an alternative to the above, the path, inclinable to the perpendicular, can be curved, in particular curved in the shape of an arc of a circle, wherein the radius of curvature chosen must be large against the deflection of the dancer roll along the curved path. A suitable ratio between radius of curvature and dancer roll deflection is about ≧3:1. With a corresponding choice of radius of curvature relative to the deflection of the dancer roll, the latter in good approximation still moves on an essentially linear path, so that the inclination angle to the perpendicular is still defined. In terms of design, this variant can be put into effect by using a swing arm, on which the bearing of the dancer roll is guided, wherein the pivot point of the swing arm for its part can be displaced to adjust the inclination angle of the path on which the dancer roll can be displaced. In particular, the adjustment unit can comprise an adjusting drive, so that the pivot point of the swing arm can be displaced along a linear essentially vertically aligned trajectory. This has the advantage that particularly with an arrangement having two adjacent deflector rolls the wrap angle, i.e. the angle at which the dancer roll is wound around by the flexible material strand, is practically constant irrespective of the position of the swing arm pivot point and therefore of the inclination angle of the path.

As an alternative to displacing the swing arm pivot point linearly, the adjustment unit can comprise an adjusting drive, the kinematics of which enable the pivot point of the swing arm, on the end of which the dancer roll is arranged, to be displaceable along a curved essentially vertically aligned trajectory. This trajectory can be predetermined by a further swing arm on which the pivot point is pivotably mounted.

When using the dancer roll to adjust the path tension with very heavy, flexible metal material strands, which require corresponding tensile forces, it can be advantageous for the at least one dancer roll to be displaced along the path, inclinable to the perpendicular, by the force effect of an actuator, in particular a hydraulic or pneumatic cylinder. This makes it possible to produce a further force, in addition to the force produced by the dancer roll itself, i.e. the downhill-slope force on the inclinable path, this further force increasing the path tension. Logically, the actuator is employed at the time when an infinitesimal inclination angle is chosen, i.e. the full weight force acts on the flexible metal material strand.

A further aspect of the present invention relates to a treatment plant for sheet-shaped metal material having a device for adjusting the tensile stress and/or for compensating variations in tension in the sheet-shaped material according to any one of claims 1 to 10.

The abovementioned advantages correspondingly apply for the treatment plant.

In terms of method, the object mentioned at the outset, using a method for operating a treatment plant for flexible metal material strands, in particular metal strips, having a device for adjusting the tensile stress and/or for compensating variations in tension in the material strand according to any one of claims 1 to 11, is achieved, when changing the material strand during continuous operation of the treatment plant, by the tensile stress being altered by adjusting the inclination angle of the path by means of the adjustment unit.

The key advantage of the method is that because the tensile force can be altered during continuous operation of the treatment plant there is no risk of sensitive material strands being damaged as a result of tensile forces being too high, since even when changing from heavy, resistant material strands to lighter, sensitive strands during continuous operation an optimum strip tension can always be set. In other respects, reference is made to the above with regard to the advantages of the method.

The invention is explained in more detail below with the aid of a drawing illustrating exemplary embodiments.

FIG. 1 shows a prior art dancer roll arrangement for sheet-shaped material, having a linearly and vertically displaceable dancer roll, in schematic side view,

FIG. 2 shows a second prior art dancer roll arrangement for sheet-shaped material, having a dancer roll held on a horizontal swing arm,

FIG. 3 shows the dancer roll arrangement from FIG. 1 with a counterweight,

FIG. 4 shows the dancer roll arrangement from FIG. 2 with a counterweight,

FIG. 5 shows the dancer roll arrangement from FIG. 2 with an actuator,

FIG. 6 shows a device for compensating variations in tension and for adjusting tensile stress on sheet-shaped material, having a dancer roll which can be displaced along a path inclinable to the perpendicular, according to a first embodiment,

FIG. 7 shows the device from FIG. 6 with an actuator for increasing the tensile stress.

FIG. 8 shows a device for compensating variations in tension and for adjusting tensile stress on sheet-shaped material, in a second embodiment, and

FIG. 9 shows a treatment plant for metal strips having a device for adjusting the tensile stress and for compensating variations in tension according to FIG. 6.

FIG. 1 shows a prior art dancer roll arrangement having a dancer roll 100 arranged between two deflector rolls 110, 120. The strip M, in the present case a metal strip, essentially horizontally guided in a strip treatment plant which is not illustrated in detail, is deflected downwards by the deflector roll 110 from the horizontal direction into the vertical direction, winds around the dancer roll 100 at a wrap angle in the region of 180° and then slightly inclined to the perpendicular is guided up to the second deflector roll 120 where it is deflected into the horizontal direction.

In the arrangement in FIG. 1, the dancer roll 100 can be displaced on a vertically aligned linear guide 130, so that almost the entire weight force of the dancer roll 100 and of its bearing 110 a acts on the metal strip M. This can lead to impermissibly high strip tensions, particularly with thin and correspondingly sensitive metal strips.

The same problem also occurs with the prior art dancer roll arrangement according to FIG. 2, in which the dancer roll 200, again arranged between two deflector rolls 210, 220, is guided at the outer end of a swing arm 230 on a circular path section, wherein the swing arm 230 for its part is pivotably mounted on a pivot point 240. As can be identified in FIG. 2, here too, the entire weight force of the dancer roll 200 and of its mounting on the swing arm 230 acts as a tensile force on the metal strip M.

Another prior art solution is illustrated in FIG. 3. Here, the weight force of the dancer roll 100 and of its bearing on the linear guide 130 acting on the metal strip M is compensated by a counter weight 140, wherein the counter weight 140 can be chosen in such a way that the resulting tensile force acting on the metal strip M corresponds to the desired value. The problem with this arrangement is that the inert mass of the dancer roll arrangement is correspondingly increased by the counterweight, so that with the compensating movements of the dancer roll 100 the inertia force both of the dancer roll 100 itself and of the counterweight 140 has to be overcome. This ultimately results in short-term variations in the strip tension, due to inertia, not being able to be satisfactorily compensated.

FIG. 4 shows the dancer roll arrangement from FIG. 2, wherein here the swing arm 230′ is extended beyond the pivot point 240 and a weight 250 can be displaced along the swing arm 230′ in such a way that by means of a corresponding resisting moment it strengthens or weakens the tensile force exerted on the strip M by the weight force of the dancer roll.

FIG. 5 again shows the dancer roll arrangement from FIG. 2, wherein here an actuator 260 in the form of a hydraulic or pneumatic cylinder acts on the swing arm 230 and consequently strengthens or also weakens the strip tensile force exerted on the strip M by the dancer roll 200 in a similar way to FIG. 4.

In FIG. 6, a device for compensating variations in tension and for adjusting the tensile stress on sheet-shaped material, in the present case a metal strip M, having a dancer roll 2 which can be displaced along a path inclinable to the perpendicular, is illustrated in a first embodiment.

The metal strip M is, to that end, guided around a deflector roll 3 and thereafter forms with the dancer roll 2 a strip loop at a wrap angle in the region of 180°, before it is again deflected via a further roll 1. In the present case, the deflection occurs in a direction inclined to the horizontal. It is, however, to be understood that a deflection into the horizontal or into another direction is equally possible.

The inclinable path of the device in FIG. 6 is in the present case designed as a linear guide 4, on which the dancer roll can be essentially frictionlessly moved by means of a sub-frame 2 a on which the bearing blocks of the dancer roll are arranged. The linear guide 4 can be pivoted by means of an adjustment unit (not illustrated in detail) comprising an electromechanical drive, in particular a spindle drive, about a pivot point X to adjust the inclination angle φ.

Thus, if for a given strip material and a given strip thickness the strip tension on the dancer roll 2 has to be preset, then the inclination angle φ is adjusted for the linear guide 4 in such a way that the tensile force F_(z) resulting from this corresponds to the required value. F_(z) is thereby calculated as

F _(z) =G·cos φ,

wherein G is the weight force of the dancer roll 2 and of its bearing and φ is the inclination angle of the linear guide 4.

The strip tension can hereby be precisely adjusted up to a maximum value, which is determined by the weight force of the dancer roll and of its bearing without using additional weights or regulating means. Short-term variations in the strip tension can be compensated in the usual way by supporting the dancer roll 2 essentially frictionlessly on the linear guide 4.

In the present case, the adjustment unit is designed to be controllable. This means that with a change in the strip thickness or width—here the ends of the strips of different thickness or width are attached to one another—the corresponding adjustment to the strip tension by changing the inclination of the linear guide 4 can be made during continuous operation of a strip treatment plant (cf. FIG. 9) prompted by a control command from the general machine control system.

In FIG. 7, the device from FIG. 6 is additionally provided with an actuator in the form of a pneumatic cylinder 5. This is used when the strip tension produced by the full weight force of the dancer roll 2 and of its bearing is not sufficient, which, for example, can be the case when treating thick and very heavy metal strips. As can be identified in FIG. 7, firstly the full weight force of the dancer roll 2 and of its bearing can be used for the strip tension if an inclination angle φ=0 is set, so that the linear guide 4 is vertically aligned. If the strip tension produced through this is still not sufficient, then an additional force can be exerted on the dancer roll 2 via the actuator 5, so that the strip tension is strengthened to the required extent. The resulting strip tensile force is therefore calculated as

F _(z) ′=G+F _(A),

with F_(A): the force exerted on the dancer roll 2 by the actuator 5.

In FIG. 8, a further device for compensating variations in tension and/or for adjusting tensile stress on a metal strip is illustrated in a second embodiment. This device differs from the one in FIG. 6, in that the dancer roll 2 cannot be moved frictionlessly along a linear unit but is suspended from a swing arm 6, the chosen length of which is long compared with the adjustment area of the dancer roll 2, so that the deflections of the dancer roll 2 when the device is in operation are in good approximation linear. A suitable ratio between radius of curvature and dancer roll deflection is about ≧3:1. The inclination to the perpendicular of this virtually linearly deflectable dancer roll 2 can now in turn be adjusted, in order to exert the desired strip tension on the metal strip M. For this purpose, the mounting of the swing arm, i.e. its pivot point, can be moved along a predeterminable trajectory by means of an adjustment unit which is not illustrated.

In FIG. 8, two differently adjusted inclination angles φ, φ′ are illustrated. In the first case, the sub-frame 6 a of the swing arm 6 is moved into a lower position A which corresponds to a comparably small angle φ≈30°. The strip tensile force which can be assigned to this angle can be calculated as F=G·cos φ. If the strip tension exerted on the metal strip M by the dancer roll 2 is to be reduced in a certain way, then the sub-frame 6 a of the swing arm 6 is moved into an upper position B by means of an adjusting drive of the adjustment unit, which corresponds to an increased angle φ′≈50°: The strip tensile force F′ in turn resulting from this is calculated as F′=G·cos φ′ and is smaller than the tensile force F calculated for position A.

It is to be understood that the movement of the sub-frame 6 a can be effected by an electromechanical drive as well as by a hydraulically or pneumatically operating cylinder (neither of which is illustrated in FIG. 8) of the adjustment unit.

The advantage of a vertically arranged linear unit 7, along which the pivot point of the swing arm 6 can be displaced, is that with the present arrangement, having two adjacent deflector rolls 1, 3, the wrap angle for the dancer roll 2 can be kept practically constant essentially irrespective of the position of the swing arm pivot point.

Finally, a treatment plant for metal strips having a device according to FIG. 6 is illustrated in FIG. 9. Here, the metal strip M, for example a copper or copper alloy strip, is unwound by a first roll 10 and firstly conducted through a furnace 12, for example an annealing furnace. Thereafter, the strip M is deflected on the roll 3 and forms a loop with the dancer roll 2, wherein the dancer roll 2 can be displaced, in the way described in connection with FIG. 6, along a path inclinable to the perpendicular about the angle φ by means of an adjustment unit which can be controlled by the general machine control system. Thereafter, the metal strip is deflected again into the horizontal around a further roll 1 and finally wound up by a second roll 10. In the current treatment plant for metal strips it is therefore possible to precisely preset the strip tension and alter it in a controlled way with modified operating parameters.

With a change in the metal strip M, which requires the strip tension to be adjusted during continuous operation of the strip treatment plant in FIG. 9, the general machine control system sends a corresponding control command to the adjustment unit to adjust the inclination angle φ of the inclinable path, whereupon the adjustment unit correspondingly adjusts the inclination angle φ, so that the dancer roll 2 always exerts an optimum strip tension on the metal strip M. 

1-13. (canceled)
 14. A device for compensating for variations in tension and/or adjusting the tensile stress on a metal material strand comprising: a metal material strand; a plurality of movable dancer rolls which the metal material strand is wound around; a path for supporting at least one of the plurality of the dancer rolls, wherein the path is capable of being inclined to the perpendicular; and, an adjustment unit for adjusting the inclination angle of the path, wherein the adjustment unit is controllable as the device is operated continuously.
 15. The device according to claim 14, further comprising: a first deflector roll and a second deflector roll located on either side of the dancer roll for winding the metal material strand around the first deflector roll, the dancer roll, and the second deflector roll thereby forming a strand loop.
 16. The device according to claim 14, wherein the path, which is capable of being inclined to the perpendicular, is linear.
 17. The device according to claim 16, wherein a bearing of the dancer roll attaches essentially without friction to the path.
 18. The device according to claim 17, wherein the adjustment unit is an electromechanical drive, such as a spindle drive or a regulating element, in particular a hydraulically or pneumatically operating cylinder, so that the path can be pivoted about a pivot point to adjust the inclination angle.
 19. The device according to claim 14, wherein the path, which is capable of being inclined to the perpendicular, is curved in the shape of an arc of a circle having a radius of curvature which is greater than the deflection of the dancer roll along the path.
 20. The device according to claim 19, wherein a bearing of the dancer roll is guided on a swing arm having a pivot point such that the pivot point of the swing arm is capable of being displaced to adjust the inclination angle.
 21. The device according to claim 20, wherein the adjustment unit comprises an adjusting drive, for displacing the pivot point of the swing arm along a linear, approximately vertically aligned trajectory.
 22. The device according to claim 20, wherein the adjustment unit comprises an adjusting drive, for displacing the pivot point of the swing arm along a curved, approximately vertically aligned trajectory.
 23. The device according to claim 14, wherein the dancer roll can be displaced along the path, which is capable of being inclined to the perpendicular, by an actuator, such as a hydraulic or pneumatic cylinder.
 24. The device according to claim 14, wherein the device is capable of compensating for variations in tension and/or adjusting the tensile stress on a metal material strand in a treatment plant for sheet-shaped metal material.
 25. A method for operating a treatment plant for flexible metal material comprising: providing a metal material strand; providing a device for compensating for variations in tension and/or adjusting the tensile stress on the metal material strand wherein the device is the device of claim 14; and, adjusting the tensile stress on the metal material strand during continuous operation of the treatment plant by adjusting the inclination angle of the path using the adjustment unit. 